To further investigate the transcription cofactor of Smad3 that regulated the transcription of PRDM16, we conducted DNA pull-down assay. we treated HK-2 cells with TGF-β and extracted the nuclear proteins. And the nuclear proteins were incubated with streptavidin magnetic beads, and biotin-labeled DNA probes which bound to the promoter of PRDM16 specifically. After repeatedly washing, the pull-down proteins were analyzed by LC-MS/MS proteomics.